properties don't serialize

get rid of properties

Properties were invented at times, when it looked like that Perl6 needs it. But this isn't true anymore. The problem with a gneral property system is that every PMC might get properties at runtime, so all PMCs share the burden all the time of a hardly used "feature". Further: a property currently is one full-blown hash per object, typically to store just one value.

The same effect can easily be achieved by using one AddrRegistry Hash to store values in it. Finaly: if some class system needs properties, it can just implement it.

attributes use external data slot (pmc_ext)

Implement differently-sized PMCs.

DYNSELF is the common case, but the common case should be SELF

DYNSELF is closer to the true OO self; if anything is worthy of the name SELF, it's DYNSELF. SELF should be renamed to something a little more static.